The invention relates to a method for processing respiratory gas of an intubated patient, wherein the humidity level of inhalation gas is raised, if necessary, before the gas is supplied to the patient. The invention also relates to an arrangement for processing respiratory gas of an intubated patient.
Respiratory gas of a patient connected to a respirator must be humidified and heated artificially since the artificial respiratory passage obtained through the insertion of a respiratory tube, i.e. through intubation, by-passes the mucous membranes of the nasal cavity where the respiratory gas becomes moist and warm during natural respiration. Dry and cold respiratory gas irritates the trachea and the bronchi and cools down the patient's body temperature.
Two principal methods have been used previously to artificially humidify respiratory gas of a patient.
The first known method is the use of active humidifiers. Active humidifiers vaporize water into the air to be inhaled from a heated container connected to the pipes on the inhalation side.
The second known method is the use of an artificial nose, i.e. a humidity and moisture exchanger (HME). The artificial nose is connected directly to the end of the respiratory tube where it recovers humidity and heat from the exhaled air and stores them for release to the next inhalation phase.
Both of the aforementioned methods are problematic. Adjustment of a simple active humidifier is based on the heating capacity and on the visual monitoring of the amount of the humidity produced in the patient's tubes. Usually the humidification is easily excessive, so that a harmful amount of water may gather in the tubes. In the aforementioned situation, the water must be removed from the tubes at regular intervals. Another problem is that the circumstances in the container of the humidifier provide an advantageous environment for the growth of bacteria. An artificial nose, in turn, can never be used to humidify excessively since only 80 to 90% of the humidity contained in the exhaled air can be recovered and utilized in the next inhalation phase. Especially patients who are in intensive care and whose secretion of mucus is heavy require additional humidity to prevent the mucus gathering in the respiratory tube from drying up. The capacity of the artificial noses is not sufficient for this. The capacity of heat recovery of the artificial noses is not always sufficient, either.